What part of Washington?
Aquarium Zen in Seattle, WA sounds like what you are looking for! Steve (owner) is a really nice guy!
Specializes in nano tanks, aquascaping, rarer plant species, etc., etc.
Most renown fish/plant/aquascaping store in Washington, and his store just opened/started not long ago! People from around the world constantly comment how they want to visit his store in person. Take a look!
Aquarium Co-op in Edmonds, WA has small fish, though I don't think Cory (owner) stocks all that many nano tanks, but most of the equipment and fish are geared toward small/nano tanks. I could be wrong though, it's been a long while since I've been up there again, and he's always getting more inventory and expanding his store and products he carries (he only carries things with good reviews/he would personally use).
Sierra Fish & Pets in Renton, WA is a bigger LFS with more fish and carries a bunch of different nano tanks and larger rimless tanks (so does Aquarium Zen).
Midway Tropical Fish & Pets in "Kent" (more like Des Moines), WA has more uncommon fish (nanos to monster fish), and also rarer shrimp (Taiwans Bees, Tigers, Crystals, etc, not the top of the line Caridina variants though).